Sized nylon yarns and method for producing same



United States Patent Patented Sept. 30, 1958 ice SIZED NYLON YARNS AND METHOD FOR PRODUCING SAME John H. Johnson and Joseph E. Fields, Dayton, Ohio, as-

signors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application October 5, 1956 Serial No. 614,061

19 Claims. (Cl. 117138.8)

This invention relates to sized nylon yarns. In some of its specific aspects, the invention pertains to an improved sizing material for use on nylon Warp yarns. In other aspects the invention pertains to improved methods for sizing nylon yarns.

This application is a continuation-in-part of our copending application, Serial No. 532,739, filed September 6, 1955, and now abandoned.

The advent of nylon yarns has presented many problems to textile manufacturers in finding a composition which can be used as an efficient sizing material. Due to the chemical and physical properties of nylon yarns, the usual materials used as sizes for natural yarns such as cotton and wool yarns and synthetic yarns of the type of viscose and acetate yarns, are not effective on nylon.

Many materials have been suggested for sizing nylon yarns. Although some have shown promise, most of those that have been suggested in the considerable period of time since the introduction of nylon yarns have fallen by the wayside.

One of the most commonly used sizes at the present time for nylon yarns is polyacrylic acid. However, it would be desirable to increase the abrasionresistance of yarns sized with polyacrylic acid. Further, since the cost of polyacrylic acid, or for that matter any synthetic sizing material, is considerable, it would be desirable to find a more etficient sizing material, i.e., one which can be used in smaller amounts to give the same or improved sizing eifects.

Among the better sizing materials for nylon yarns are to be found copolymers of vinyl acetate with maleic anhydride, the partial alkyl esters thereof, and certain other derivatives of vinyl acetate/maleic anhydride copolymers. However, even with these materials the adhesion to the nylon and the abrasion resistance are such as to leave considerable room for improvement.

The use of a wide variety of tacky film-forming materials has been recommended for sizing nylon yarns. This recommendation required that such film-forming material be tacky in the air-dried state in accordance with a test whereby a No. 9 lead shot is dropped from a height of 1 centimeter onto a freshly prepared film of the composition having a thickness of approximately 0.2 mm. and which has been dried for 24 hours at a temperature of 25 C. and a relative humidity of 50%; if, upon inverting the film, the lead shot does not fall free within a period of seconds, the composition is considered to be tacky in the air-dried state. Included in such tacky film-forming materials were a wide variety of compositions, including various alkyd resins, copolymers of olefin hydrocarbons and maleic anhydride such as ethylene-maleic anhydride interpolymers which were hydrolyzed by reaction with aqueous caustic to form the partial or complete sodium salts, certain methacrylate polymers, natural resins and carbohydrates. None of these tacky materials has found commercialapplication in the'sizing of-nylon yarns.

2 An important drawback of many materials used for sizing nylon is that supplementary additives are essential to obtain results suificiently satisfactory to permit practical use. Such supplementary materials include lubricants, wetting agents, urea, etc. These not only increase the cost of the sizing composition butoften make the removal of same, after the weaving operation, much more diflicult. Thus, the scrubbing operation for removal of size takes longer and is more expensive when an oily lubricant has been used. Another drawback of conventional nylon sizes is that after-waxing is usually required. This involves applying the size, drying the sized yarn, and then applying a wax to the sized yarns before they can be used in knitting machines. Again, the cost is increased, and the scrubbing operation made more diflicult. i

In accordance with the presentinvention, nylon is sized with a water-soluble free acid form of an olefin/maleic interpolymer having from zero to 100 percent of its maleic units mono-esterified with an alkanol, said olefin having from 2 to 3 carbon atoms, the said interpolymer in said free acid form having a specific viscosity of at least 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C.; the C -C olefin employed in forming said interpolymer can be ethylene, propylene, or a mixture of ethylene and propylene in any proportion, and hereinafter this is to be understood wheni ever reference is made to olefin/maleic interpolymers. These materials are absolutely non-tacky, even under humidity conditions much more severe than those set forth in the aforementioned test for tackiness. In contrast, the alkali metal salts, e. g., the sodium salts, of

some of these materials, particularly those of low molecular weight, tend towards tackness and the higher the humidity the more tacky they become' The alkali metal salts are also also found to be far inferior as nylon sizing agents, and in fact are of no practical interest whatsoever to those concerned with the sizing and weaving of nylon yarns. It is essential in the practice of the inven tion that the olefin/maleic interpolymers be employed in their non-tacky free acid form.

In preferred embodiments of the invention, nylon yarn is sized with ethyl'ene/maleic anhydride copolymer, propylene/maleic anhydride copolymer, or ethylene-propyl'ene/maleic anhydride copolymer, which has been converted to water-soluble free acid form. This is very readily accomplished simply by dissolving the olefin/ maleic anhydride interpolymer in warm water, e. g., by introducing the anhydride form of the interpolymer in the desired quantity into water heated to say C; and vigorously agitating same; this will permit complete solution to occur within a period of approximately one hour or less in the case of ethylene/maleic anhydride copolymer and in a somewhat longer time (say 60 to 9Q minutes) in the case of propylene/maleic anhydride copolymer. The result is an aqueous solution of the interpolymer in water-soluble free acid form, most or all the anhydride groups under these conditions being hydrolyzed to form two carboxylic acid groups per maleic anhydride group originally present in the molecule, Some mill operators will prefer to receive the polymer in the anhydride form, paying lower freight costs, and put it into solution, as just described, at the mill. Others, however, will prefer that the olefin/maleic anhydride interpolymer be hydrolyzed as a separate operation prior to its shipment to the place of use as a sizing agent. This is readily done by the solution procedure just described, followed by drying the aqueous solution, e.- g., by spray drying or in a tray-type drying oven under a vac uum and at moderate temperatures from say 50 to 90 C. A more desirable physical form of the solid water-solu ble free acid polymer, however, is obtained by subjecting the polymer in its anhydride form to the action of waterv vapor. For example, the anhydride form of the ethylene copolymer can be subjected to a relative humidity of 70 to 90 percent, at a temperature of 50 to 90 C., for a period ranging from one-half hour to say 5 to hours sufficient to effect hydrolysis of an adequate number of anyhydride groups to carboxylic acid groups to give the polymer the property of prompt water solubility; somewhat more stringent conditions and/or longer time are used for the propylene copolymer. It is preferred to effect this vapor-phase hydrolysis until substantially complete hydrolysis to the free acid form has occurred. In any event, the olefin/maleic anhydride interpolymer is prepared by interpolymerizing a C -C olefin material with maleic anhydride under such conditions as to give a polymer in the anhydride form which, on hydrolysis to free acid form, exhibits a specific viscosity of at least about 0.1 as determined on a one weight per cent solution thereof in dimethyl-formamide at 25 C. Generally speaking, such an interpolymer having a specific viscosity determined in the same way on the anhydride form, of about 0.05 to 0.07 will have in the free acid form the desired minimum specific viscosity of about 0.1. In general, the specific viscosity of the free acid form of a C -C olefin/maleic anhydride interpolymer will be somewhat less than twice the specific viscosity of the same polymer in the anhydride form. Olefin/maleic anhydride interpolymers which have been hydrolyzed in any manner to the free acid form consist essentially of regularly recurring units of the formula R CHr-(LH-CH-CH- wherein R is H in the case of ethylene, is CH, in the case may contain some umts wherein R is H and some wherein R is CH In order to impart added desirable properties, particularly for certain special sizing applications, we can prepare an olefin/maleic interpolymer having a portion, up to 100 percent, of its maleic units mono-esterified with an alkanol, preferably by reacting an olefin/maleic anhydride interpolymer with a lower fatty alcohol, e. g. methanol, ethanol, isopropanol, n-propanol, n-butanol, sec.- butanol, tert.butanol, isobutanol, the various amyl alcohols, etc. Higher alcohols such as those containing from 8 to 10, 15, or even or more carbon atoms per molecule, of any of the possible straight-chain or branched-chain configurations, and constituting primary, secondary, or tertiary alcohols, can also be used for special situations, but in general a lesser percentage of the maleic units shouldbe esterified with such higher alcohols than in the case of the lower alcohols. The esterification is readily effected by mixing the olefin/maleic anhydride interpolymer with the chosen alcohol or a mixture of alcohols, and refluxing the mixture till the desired degree of esterification is achieved.

An alternative, but generally less desirable, preparation of an olefin/maleic interpolymer having at least a portion of its maleic units mono-esterified with an alkanol, involves interpolymerizing a C C olefin material with a comonomeric material comprising a monoalkyl maleate, e. g., monomethyl maleate, monoethyl maleate, mono-isopropyl maleate, mono-n-butyl maleate, monododecyl maleate, or the like, wherein the esterifying alcohol moiety is as described above. These materials can also be described as monoalkanol esters of maleic acid, or as acid esters of maleic acid. In the limiting case, the comonomeric material to be copolymerized with the C C, olefin consists entirely of monolkyl maleate. It is preferred thatthe comonomeric material also comprise maleic anhydride, so that the olefin is interpolymerized with a mixture of maleic anhydride and one or more monoalkyl maleates. It is also to be understood that where the comonomeric material consists of monoalkyl maleate, such monoalkyl maleate can be a single species or a mixture of monoalkyl maleates.

In any event, whenever maleic anhydride units are present in the interpolymer, the interpolymer is subjected to hydrolysis under conditions converting same to free acid form. The polymers presently preferred in the practice of the present invention are C -C olefin/ maleic interpolymers having from zero to 50 percent of the maleic units therein mono-esterified with an alkanol, by which language is understood the esterification can be by virtue of esterifying maleic anhydride units in a pre prepared interpolymer and/or by the use of monoalkyl maleate as a comonomer in preparing the polymer.

Regardless of the present or absence of mono-esterified maleic units in theinterpolymer to be used, the interpolymer in free acid form should be water soluble, i. e., at least 1 part by weight can be dissolved in parts by weight water at 20 C., and should have a specific viscosity of at least about 0.1 determined as hereinabove mentioned. All of the specific viscosities referred to here are determined on the polymer in its free acid form, in a one weight per cent solution of the polymer in dimethylformarnide at 25 C. In most instances the polymer used will have a specific viscosity within the range of about 0.3 to 4 although those of even higher specific viscosity than 4 are within the broad scope of the invention. In general, the higher molecular weight polymers are more effective than the lower molecular weight; hence we often prefer to employ those which have a specific viscosity of at least about 1. However, when the sized nylon yarn is to be subjected to heat greater than that required merely to dry the yarn, for example when very fast drying is obtained by use of high temperatures or when the woven fabric is heat-set, such as at temperatures above BOO-350 F., the higher molec ular weight copolymers tend to become difficult to remove by subsequent washing so in such instances we generally prefer to use the copolymers having specific viscosities below about 1. Furthermore, in such instances of heat setting, we find the propylene/maleic copolymers to he apparently much less reactive with the nylon and thus much more easily removable by washing than the ethylene/maleic copolymers, and hence the propylene/maleic copolymers are preferred under these circumstances. The following examples illustrate some features and advantages of the invention. It will be understood of course that variations from the exact details shown can be made without departing from the invention.

EXAMPLE 1 1600 ml. benzene, 200 grams maleic anhydride and 2.56 grams benzoyl peroxide. It was charged with ethylene to give a pressure of 500 pounds per square inch gauge, and was maintained at this pressure during the reaction. The reaction temperature was maintained at 70 C.

When polymerization had ceased, as evidenced by no further tendency of the pressure to drop, excess ethylene was bled off and the reactor opened. The ethylene/ maleic anhydride interpolymer, present as a slurry of fine particles in benzene, was separated by filtration and dried in a vacuum oven at C. for about 20 hours. The yield of interpolymer was 255 grams, which was 99% of theory, based on maleic anhydride charged.

The specific viscosity of this ethylene/maleic anhydride interpolymer, as determined on a one weight percent solution thereof in dimethylformarnide at 25 C., was 1.26.

(B) In the same apparatus and by the same procedure as described in A, the autoclave was charged with 1600 ml. of benzene, 200 grams of maleic anhydride and 2.56 grams of benzoyl peroxide (0.26 mole percent based on theoretical reacting monomers). Polymerization temperature was 60 C. Ethylene was charged to give a pressure of 400 pounds per square inch gauge, and this pressure was maintained throughout the polymerization by additional charging of ethylene when required.

The ethylene/maleic anhydride interpolymer was recovered as in A, in a yield of 252 grams, which was 98% of theory based on maleic anhydride charged.

The specific viscosity of the interpolymer, determined in the same way, was 1.293.

(C) A blend of the ethylene/maleic anhydride interpolymers of A and B above was prepared in a total weight of 400 grams. The specific viscosity of the blended polymer, as obtained by averaging the specific viscosities of the two polymer preparations of A and B, was about 1.28.

This blend was exposed in trays in a closed oven to a temperature of 70 C. and an air atmosphere of 70% relative humidity. After a little over 7 hours time, substantially complete hydrolysis of the maleic anhydride units in the interpolymer had occurred, and the resulting free acid form of the interpolymer was completely watersoluble.

The specific viscosity of the hydrolyzed free acid form of the ethylene/maleic interpolymer whose preparation has just been described, was determined on a one weight percent solution thereof in dimethylformamide at 25 C. The specific viscosity of the free acid form determined under these conditions was 2.22.

EXAMPLE 2 (A) In the manner of Example 1, ethylene and maleic anhydride were interpolymerized in three separate batches, using benzene as diluent, lauroyl peroxide as catalyst, ethylene pressure maintained at 600 pounds per square inch gauge and a reaction temperature of 50 C. The three batches were then mixed together in the slurry form before filtering. The filtered polymer was Washed several times with benzene, and dried in a 100 centigrade oven for 24 hours under vacuum. The specific viscosity of this ethylene/maleic anhydride copolymer, determined on a one Weight percent solution thereof in dimethylformamide at 25 C., was 1.57.

(B) As described in paragraph C of Example 1, the interpolymer whose preparation is described in paragraph A of this Example 2, was subjected to hydrolysis by being maintained at conditions of 70 C. and 70% relative humidity until complete conversion to the free acid form resulted. This material was freely soluble in water. The specific viscosity of the thus-hydrolyzed water-soluble free acid form as determined on a one weight percent solution thereof in dimethylformamide at 25 C., was 2.71.

EXAMPLE 3 The effectiveness of the products of Examples 1 and 2 as size for nylon yarns was determined. To conduct the test, a 5 to 6 weight percent aqueous solution of each of the polymers was prepared. Nylon (polyhexamethylene-adipamide) warp yarns of 70 denier, 34 filament, and 7 Z twist, were drawn through the solution at a rate of about 10 to yards a minute and then passed through squeeze rolls adjusted to exert a pressure of about 10 to 20 pounds per linear inch. The yarns were then dried by passing them over a series of five metal drying cans being respectively at 180 F., 200 F., 200 F., 200 F., and 160 F. No sticking of the size or coated yarns occurred during the drying process.

Yarns thus treated have a sizing of about 2 to 4 percent by Weight of the interpolymer firmly adherent thereto. The sizings are tough and abrasion resistant. The

' 6 sized. yarns may be woven easily and efiiciently using standard weaving techniques.

The abrasion resistance of nylon yarns sized with the interpolymers of this invention was tested in a standard abrasion testing apparatus with the results being reported on arbitrary units ranging from 10 to 1, with 10 being nearly perfect resistance to abrasion and 1 being substantially no abrasion resistance. The effectiveness of the interpolymers of Examples 1 and 2 as nylon sizes was compared with the effectiveness of other polymers, by the same abrasion resistance measurements on the same kind of nylon yarns sized in the same way. The polymer materials tested were:

Material Description Example 1 product.

Example 2 product.

Terpolymer of vinyl acetate, maleic anhydride, and a partial methyl ester of maleic acid.

Terpolymer of vinyl acetate, maleic anhydride, and a different partial ester of maleic acid (found to be supea nylon size.

The following results were obtained:

It can be seen that the nylon yarn sized with materials A and B suffered practically no loss in abrasion resistance throughout the entire test period of cycles in the abrasion tester. The next best material, i. e., material G, held up in abrasion resistance through 20 cycles, but at 40 and 80'cycles showed progressively lower abrasion resistances. Materials A and B even at 80 cycles were superior in abrasion resistance to material G at 40 cycles. The vinyl acetate/maleic anhydride terpolymers (materials C, D and E), and the vinyl acetate/maleic anhydride copolymer (material F), all sufiered from considerable to extreme loss in abrasion resistance as the number of cycles increased, and none was comparable with materialsA and B.

EXAMPLE 4 A large sample of ethylene/maleic anhydride interpolymer converted to the free acid form, was obtained by combining a number of batches, whose preparation is typified by the following, the parts being by weight. Into a large stirred pressure-resistant reactor were charged 8060 parts benzene, 1570 parts maleic anhydride, 31 parts benzoyl peroxide, and 675 parts ethylene. The reactor was maintained at 64-67C. for a period of 15 hours, during which time an additional 422 parts ethylene was charged to maintain the reaction pressure within the range of 260-275 pounds per square inch gauge. This 422 parts ethylene was 94 percent of that theoretically required to copolymerize (in 1:1 mole ratio) with the maleic anhydride.

At the end of 15 hours, the excess ethylene was blown down, and the ethylene/maleic anhydride interpolymer recovered, from the polymer-benzene slurry by filtration. It was then washed with benzene, then dried at l10 C'. in: vacuo giving the polymer in the anhydride fonn as a fine white powder. The combined batches had a specific viscosity (1 weight percent solution in dimethylformamide at 25 C.) of 0.597

The polymer was then exposed to an atmosphere of 70% relative humidity at 70 C. until a sample proved to be promptly and freely soluble in cold water without any cloudiness of the resulting solution. The thus-hydrolyzed polymer, which was the ethylene/maleic anhydride polymer in free acid form, had a specific viscosity of 0.928 as determined on a 1 weight percent solution thereof in dimethylformamide at 25 C.

EXAMPLE 5 The free acid form of ethylene/maleic anhydride interpolymer whose preparation is described in Example 4, was employed in a commercial textile mill to size 70 denier, 34 filament, S-turn semi-dull nylon warp yarns going into a 96 inch by 72 inch taffeta weave. The filling yarn for the tafieta weave was.also 70/ 34/ 5 nylon yarn. The interpolymer, in the proportion of 70 pounds per 100 gallon-s water, was added to cold water with agitation and the resulting slurry was heated to 160 F. After heat and agitation had been maintained for approximately 25 minutes, a check of the solution showed that the interpolymer had dissolved completely. The size box temperature was 140 F. The drying cylinders were at 140, 150, 180, 180, 180, and 180 F. The squeeze roll pressure and slasher speed were respectively 900 pounds per linear inch and 35 yards per minute. There were 4656 ends in the warp.

The sized warp yarn was not afterwaxed. The importance of this will best be understood when it is noted that it is the practice in the mills to apply a wax-like material to sized nylon yarn as it rolls otf the last drying cylinder. The wax is usually hydrogenated animal fats which add lubricity to the yarn. This lubricity will make the yarn slide through the reeds and heddles with diminished shedding of size. Afterwaxing is an added operation in sizing. must scour the woven cloth to remove the wax and size, the scouring operation being longer when wax is on the cloth. It would be advantageous, therefore, if the sizing agent would perform well on nylon without any aid from afterwaxing. The mill tests reported in this example were carried out without any benefit of afterwaxing, and thus represent a severe test of the ability of the polymer to size nylon warp yarns effectively. (Although lack of necessity for afterwaxing is an important advantage of the invention, it is of course not out-side the broad scope to afterwax where under certain circumstances economics warrant it, for example when extra heavy pick-up is used, or when it is desired to size an unusually long warp.)

The following conclusions were reported by those operating this mill test.

Size preparation No difliculty was encountered in the handling or mixing of the size solution. The dry powdered form, which easily went into solution, was much preferred to the form in which polyacrylic acid is made available to the mills, namely in a 25 percent aqueous solution. The size solution of this mill test foamed some in the kettle and the size box, but this dissipated rapidly and caused no trouble.

slashing Thesized yarn was satisfactory in all respects in the It is also added work to the finisher who,

8 weaving operation, including weaving efiiciency and seconds. No shedding of the size occurred, and the yarn appeared to be well protected from abrasion. Significant improvements in the finished characteristics of the scoured fabric, such as appearance of the face of the cloth, were noted over the same characteristics of the identical kind of fabric made from polyacrylic acid sized yarn which was finished at the same time under identical conditions by sewing the fabrics together and processing them together.

EXAMPLE 6 In the same apparatus and by the same general procedure of Example 1, the autoclave was charged with 1600 ml. ethylene dichloride, 196 grams maleic anhydride, 27.6 g. n-butyraldehyde (to lower the molecular weight of the copolymer), and 168 g. propylene. The propylene/maleic anhydride mole ratio was 2:1 and the catalyst was 0.25 mole percent. Initial pressure in the bomb at the reaction temperature of 70 C. was about '75 p. s. i. g.

The temperature was maintained at 70 C. overnight. Unreacted propylene was then bled oif and the autoclave opened. The propylene/maleic anhydride interpolymer was filtered, washed with ethylene dichloride, and dried in a vacuum oven at 110 C. for 12 hours. The yield was 90.4 percent of theory.

The specific viscosity of this interpolymer, in the unhydrolyzed (anhydride) form, as determined on a one weight percent solution thereof in dimethylformamide at 25 C.,' was 0.28.

This interpolymer was put into solution and hydrolyzed to the free acid form for use as a nylon size (as described in Example 7 below) by admixture with water and heating to the boiling point for one to two hours.

EXAMPLE 7 The effectiveness as size for nylon yarn of the product of Example 6, and for comparison purposes a commercial polyacrylic acid nylon size, was determined by the same general sizing and testing procedures described in Example 3. The size bath concentration was 4 percent solids, i. e., the yarn was sized by being drawn through a 4 weight percent aqueous solution of the polymer being tested. The size add-on was 1.9%, i. e., the sized yarn after drying carried the polymer in the amount of 1.9% by weight of the yarn. These and other conditions differed somewhat from those employed in Example 3, so the abrasion resistance values of this example are not directly comparable with those given in Example 3. However, the data of this example are consistent within themselves.

The following results were obtained:

Abrasion Resistance It can be seen that with increasing abrasion, the resistance of the yarns fell oif at different rates so they were equal at 40 cycles and the propylene/maleic 'copolymer was superior at cycles. During the entire test period of 80 cycles in the abrasion tester, the commercial size lost 3.0 points in abrasion resistance while the product of Example 6 lost only 2.2 points.

The interpolymer-s employed in the present invention are readily prepared by a variety of polymerization procedures. Preferably, the C -C olefin, by which we mean ethylene, propylene, or mixtures thereof, is interpolymerized with maleic anhydride, or with maleic anhydride plus one-or more monoalkyl maleates, or with one or more monoalkyl maleates in the absence of maleic anhydride, in the presence of a liquid organic diluent and a free radical liberating catalyst.

The following preferred reaction conditions refer particularly to the copolymerizations with maleic anhydride. When substituting monoalkyl maleate for part or all of the maleic anhydride, somewhat more stringent conditions, i. e., higher temperature, higher pressure, and/or higher catalyst concentration, may be required since the monoalkyl maleates enter into the interpolymerization reaction somewhat less easily than does maleic anhydride.

We prefer to employ a reaction temperature within the range of 40 to 90 C., and 45 to 80 C. is especially advantageous. At such temperatures, the reaction rate is good and the physical form of the interpolymer product is good. However, temperatures outside these limits can be used.

The reaction pressure can be atmospheric or below, but is preferably superatmospheric. With any chosen combination of reaction conditions, propylene can be used at appreciably lower pressures than ethylene, say from 50 to 500 pounds per square inch lower pressure to obtain equivalent olefin concentration in the reaction mixture. It is preferred that the reaction be carried out in a closed vessel such as a stirred autoclave, rocking bomb, tubular reactor through which reaction mixture flows, or the like, at a pressure above atmospheric pressure. The pressure is preferably above 20 pounds per square inch gauge (p. s. i. g.) in the case of propylene, and above 100 p. s. i. g. in the case of ethylene, and pressures of 200 to 600 pounds per square inch gauge are especially preferred in the latter case. However, even higher pressures, say up to 1000 pounds per square inch, or even higher such as up to 5000 pounds per square inch and above, are permissible. In general, the higher the temperature the lower the molecular weight, and the higher the pressure the higher the molecular weight.

The copolymer product contains essentially one mole of total olefin per one mole of maleic anhydride combined therein, irrespective of the relative proportions of ethylene or propylene or mixtures thereof on the one hand and maleic anhydride on the other hand, introduced to the reaction system. The ratio of free olefin, available for reaction, to free maleic anhydride available for reaction, at any given time depends upon a variety of factors, including particularly the quantity of free maleic anhydride dissolved in the solvent and the quantity of olefin dissolved in the solvent. The latter value in turn depends upon the solubility of olefin in the reaction mixture, which is a function of the particular solvent, the temperature, the pressure, and the concentration of maleic anhydride in the solvent. It is much preferred that by the time the reaction has been completed an excess of ethylene over that required to react with the entire quantity of maleic anhydride shall have been furnished to the reaction mixture, so as to give maximum utilization of the maleic anhydride. Any unreacted ethylene is readily recovered and recycled to the reaction. This is less necessary with propylene and with this olefin an effective manner of operating is to charge initially all the maleic anhydride and less than the stoichiometric amount of olefin and intermittently or continuously add olefin until the total charged is just equal to or slightly more than the stoichiometric quantity.

The C -C olefin, maleic anhydride, and solvent or diluent, can be brought together in various ways, but in any event thorough intermixture of same should be provided. Thus, the reaction can be conducted in a batch, into which the olefin is continuously or intermittently added to maintain pressure until all the maleic anhydride is used up by copolymerization. A similar operation can be conducted wherein maleic anhydride is added continuously or intermittently. The components of the reactionrnixture, can be continuously fed intoa stirred autoclave with continuous overflow of total reaction mixture out of the autoclave either through recovery steps or through a series of autoclaves'. The total reaction mixture can be passed through an elongated reaction tube, with olefin and/or maleic anhydride and/or catalyst being added at one or more points along the length of the tube if desired.

It is most convenient to carry out the polymerization reaction in the presence of an organic solvent for the maleic anhydride. Such solvent is preferably also a nonsolvent for the copolymer product. Such materials, which can be termed solvents or diluents, are advantageously aliphatic or aromatic hydrocarbons or chlorinated hydrocarbons, for example benzene, toluene, xylene, n-hexane, mixed hexanes, octane, dichloroethylene and the like. While the proportion of the diluent to the other components of the reaction mixture can be varied over a wide range, it is prefelred to employ an amount such that the final reaction mixture will have a solids content (calculated on the assumption that all maleic anhydride has copolymerized) within the approximate range of 5 to 60 weight percent.

In instances where the lowest molecular weight polymers are desired, especially in the case of ethylene/maleic anhydride copolymers having (in the free acid form) specific viscosities below about 0.3 and in the case of propylene/maleic anhydride copolymers having (in the free acid form) specific viscosities below about 0.5, the copolymerizations can if desired be effected in the presence of certain added materials that result in a lowering of the molecular weight of the copolymer product. Thus, the copolymerization can be effected in the presence of an aldehyde having the formula wherein R is selected from the group consisting of hydrogen, hydrocarbon radical-s, and aldehyde-substituted hydrocarbon radicals, and preferably such aldehydes having at least one hydrogen atom on the ix-carbon atom, for example butyraldehyde, as disclosed and claimed in the copending application of John H. Johnson, Serial No. 603,211, filed August 10, 1956; a suitable quantity is from 0.5 to 20 mole percent of the aldehyde, based on the reacting monomers (assuming percent conversion), i. e., from 0.5 to 20 moles of the aldehyde per 50 moles maleic anhydride charged (50 moles maleic anhydride will theoretically react with 50 moles of the olefin, thus making 100 moles of reacting monomers). Another class of materials that can be present during the, copolymerization in order to lower the molecular weight of the product constitutes the R-dihydrogen phosphites and di-R-hydrogen phosphites wherein R is a monovalent hydrocarbon radical, for example dibutyl hydrogen phosphite, as disclosed and claimed in the copending application of John H. Johnson, Serial No. 584,175, filed May 11, 1956; a suitable quantity is from 0.5 to 10 mole percent of' the phosphite, based on the reacting monomers. Still another suitable method for preparing low molecular weight copolymers is to effect the copolymerization in the presence of an inert liquid solvent for maleic anhydride selected from the group consisting of benzene, halobenzines, and haloparaffins, plus an alkylated aromatic hydrocarbon having at least one tat-hydrogen, for example a mixture of benzene and p-cymene or a mixture of ethylene dichloride and diisopropylbenzene, as disclosed and claimed in the copending application of John H. Johnson, Serial No. 603,212, filed August 10, 1956; suitable quantities are from 10 to 300 mole percent of the alkylated aromatic hydrocarbon having at least one ochydrogen, based on the reacting monomers, plusv sufilcient of the inert liquid solvent to maintain all the maleic anhydride charged to the process in solution in the reaction mixture at the reaction conditions and to give a finalreaction mixture of desired solids content.

The copolymerization'is effected in the presence of a catalyst of free radical-promoting type, principal among which are peroxide-type polymerization catalysts and azotype polymerization catalysts. Those skilled in the art are now fully familiar with a large number of peroxidetype polymerization catalysts and a suitable one can readily be chosen by simple trial. By way of example there can be mentioned benzoyl peroxide, tertiary butyl peroxide, tertiary butyl hydroperoxide, diacetyl peroxide, diethyl peroxycarbonate, dimethylphenylhydroperoxymethane (i. e., cumene hydroperoxide), hydrogen peroxide, potassium persulfate and the like. The azo-type polymerization catalysts are also well known to those skilled in the art. These are characterized by the presence in the molecule of the group N=N wherein the indicated valences can be attached to a wide variety of organic radicals, at least one however preferably being attached to a tertiary carbon atom. By way of example there can be mentioned a,a-azodiisobutyronitrile, azomethane, diazoaminobenzene, and the like. The peroxytype or azo-type or other free radical-promoting type of polymerization catalyst is used in small but catalytic amounts, which generally are not in excess of one to two mole percent based on moles theoretical reacting monomers charged, i. e., based on the sum of the moles maleic monomer charged plus the same number of moles olefin when the latter is present in at least the stoichiometric amount. A suitable quantity is often in the range of 0.1 to 1.0 mole percent.

The foregoing discussion of solvents, catalysts, added materials for lowering molecular weight, reaction systems, etc., is also applicable to interpolymerization of ethylene, propylene or their mixtures, with comonomeric materials comprising monoalkyl maleates.

The interpolymer, however made, is advantageously separated from'the bulk of the solvent by filtration or centrifuging, and then subjected to mild heating, preferably at sub-atmospheric pressures, for example at temperatures of 50 to 100 C., to remove residual solvent. It is often advantageous to precede this drying step by a washing step in which any unreacted maleic monomer is washed from the polymer by use of a solvent such as benzene.

In the event maleic units in the olefin/maleic interpolymer are to be mono-esterified by after-reaction of an interpolymer containing maleic anhydride units with an alkanol, this esterification reaction can be effected, for example, by adding to the slurry of polymer in solvent the calculated quantity of alkanol required for the degree of esterification desired and heating until esterification is substantially complete (e. g., 4-5 hours at reflux).

As pointed out hereinbefore, any interpolymer containing maleic anhydride units is subjected to hydrolysis to convert the maleic anhydride units to free acid form, prior to use of the polymer as a size for nylon. It is preferred to effect the hydrolysis as a preliminary step,

preferably by contacting the interpolymer with water vapor under conditions resulting in hydrolysis of essentially all the anhydride groups to dicarboxylic acid groups. Or the hydrolysis can be effected by contacting a slurry of the interpolymer in an organic solvent with water, or merely by mixing the interpolymer with water until it undergoes hydrolysis and dissolves in the water. The resulting solution can be used directly as the size, or it will frequently be dried by conventional means and the resulting solid free acid form of the interpolymer then shipped to the mills for use as a size.

It is essential to the practice of the invention to employ the interpolymer in the water-soluble free acid form. To this end, the extent of monoesterification of ma'leic groups in the interpolymer must be limited, and the greater the number of carbon atoms in the alkanol employed for esterification (or employed as esterifying moiety of a monoalkyl maleate monomer), the smaller the percentage of maleic units in the interpolymer that can be esterified and still have an interpolymer which is water-soluble in the free acid form, unless the esterifying alcohol contains water-solubilizing groups (e. g., monoethers of polyethylene glycols). Some of the benefits of the invention can be retained even though an alkali, such as sodium or potassium hydroxide, be employed in solubilizing the interpolymer (which may sometimes be desirable when part or all the maleic units are esterified), so long as such quantity is very small in amount, say not over 0.2 mole sodium hydroxide per mole of maleic units in the interpolymer. The interpolymer under such conditions is still considered to be in the free acid form. However, the use of much more alkali results in the presence of too high a proportion of the sodium salt in the sizing material. The sizing efliciency drops off rapidly as the percentage of salt increases and very much of the salt completely spoils the sizing efiect. Accordingly, it is much preferred to add no alkali or other salt-forming cation whatsoever. Naturally, industrial waters used in making up the size will generally contain a limited amount of cations (and associated inorganic anions and/ or hydroxyl ions), and the use of such waters is not outside the scope of the invention. However, the more ion-free the water used in dissolving the interpolymer to make up the size solution, the more satisfactory the results. It may be mentioned here that C -C olefin/maleic anhydride copolymers converted to the free acid form dissolve in water to give aqueous solutions having a pH of about 2.2 to 2.5.

The C -C olefin/maleic interpolymers employed in the water-soluble free acid form in the present invention are unique materials. As pointed out elsewhere, the sodium salts of these polymers are wholly unsatisfactory as nylon sizes. Further, the materials employed in this invention are superior to other maleic copolymers, such as vinyl acetate/maleic anhydride copolymers, and they are superior to polyacrylic acid. It is interesting to note that both polyacrylic acid, and hydrolyzed ethylene/maleic anhydride interpolymers used in the present invention, contain two carboxylic acid groups per four carbon atoms in the polymer chain (the propylene interpolymers of course contain also two such groups per four carbon atoms in the chain and per five carbon atoms in the polymer). However, the groups are positioned differently, those in the copolymers of the present invention being in pairs wherein two carboxylic acid groups are immediately adjacent, as opposed to the carboxylic acid groups in polyacrylic acid which are regularly separated from each other by a CH, group in the polymer chain. We have found that all the carboxylic acid groups in polyacrylic acid titrate similarly as one. We have foundon the other hand that with our hydrolyzed olefin/maleic anhydride copolymers, the carboxylic acid groups are of two distinctly different acid strengths; thus, the titration curve shows two inflection points. Another remarkable difference we have observed by comparing, for each of the two types of polymers, the specific viscosities in an organic solvent with the specific viscosities of the same polymer in water. With two polymers, one being polyacrylic acid and the other the free acid form of an ethylene/maleic anhydride copolymer, having the same specific viscosity as measured in an organic solvent such as dimethylformamide, the specific viscosity of the latter polymer in water is much higher than that of the polyacrylic acid in water, and this difference increases with increasing molecular weights. This can be interpreted to mean that, in water, the ethylene/maleic anhydride copolymer (free acid form) is much more highly extended than is the polyacrylic acid molecule of the equivalent molecular weight. In fact, the viscosity data indicate that polyacrylic acid is highly coiled in water solution. The extension of the ethylene/maleic free acid polymer in water we believe to be due to the greater repulsion between the carboxyl groups, which are adjacent in this polymer rather than separated as in polyacrylic acid. The resulting more extended molecule offers a greater number of sites for bonding than does the coiled molecule, the advantage for the interpolymers of the present invention being approximately 2 to 1 over polyacrylic acid. This, in turn, is believed to lead to improved cohesion or adhesion with the nylon fibers, which is one possible explanation of the reduced shedding experienced in use of our interpolymers as nylon sizes, and the fact that there is ordinarily no need for other modifying additives being present, or for employing the technique of after waxing.

In practice, the water-soluble free acid form of an olefin/maleic interpolymer as described herein is dissolved in water to form an aqueous solution which preferably, though not necessarily, contains from about 2 to about 15 percent by weight of the interpolymer. For the best results, the size solution should be used or applied to the nylon yarn at a temperature between about 100 and 200 F. At these temperatures, the size solution is less viscous and penetrates into the yarn more readily and uniformly.

The size solution is supplied to the yarn in an amount and in a concentration suflicient to deposit a sizing quantity of the interpolymer on the yarn, preferably between about 0.5 and 10 percent by weight of the interpolymer based on the dry weight of the nylon yarn. This may be accomplished in various ways, for example by passing the yarns through the size solution and beneath the surface thereof or by spraying the yarns with the size solution, and thereafter passing the yarns between squeeze rolls to remove excess solution and to deposit the required amount of the interpolymer. The size solution may also be applied in other ways, for example by dipping the yarns into a solution of the interpolymer. If squeeze rolls are used, the amount of pressure exerted upon the squeeze roll should be adjusted to remove sufiicient excess solution to deposit the required sizing amount of interpolymer on the yarn.

The size solution may contain, in addition to the interpolymer, small amounts, say 0.01 to 5 weight percent, of sizing adjuncts such as urea, humectants, oils, wetting agents, and the like. As examples of humectants may be mentioned glycerine, ethylene glycol, sorbitol propylene glycol, polyethylene glycols, polyglycerols, polypropylene oxides, and the like. Oils which may be used include the sulfonated animal, mineral and vegetable oils or mixtures thereof, water-emulsifiable mixtures of such oils with animal oils, mineral oils, vegetable oils, Twitchell oil, and the like. As examples of wetting agents may be mentioned acid-stable anionic wetting agents such as alkyl substituted benzene sodium sulfonates, in which the alkyl group contains from about to 20 carbon atoms, alkali metal or ammonium monoalkyl sulfosuccinates, in which the alkyl group contains from about 10 to 20 carbon atoms, and the like; and acid-stable non-ionic wetting agents such as the surface active condensation products of ethylene oxide with an alkylated phenol having from 8 to 20 carbon atoms in the alkyl group or an alkyl mercaptan having from 8 to 20 carbon atoms.

However, a very important advantage of the present invention is that such sizing adjuncts as have been discussed, are entirely unnecessary for the obtaining of eminently satisfactory results. This is in distinct contrast to standard commercial practice wherein, with most sizes for nylon, one ormore such adjuncts are essential ingredients of the sizing solution.

The treated nylon yarns may be dried in various ways. Thus, they must be air-dried at normal room temperatures, that is, between about 65 and 85 F. However, it is preferred to dry the treated yarns at elevated temperatures of about 140 to 250 F. This may be accomplished by passing the treated yarns through an oven in which the circulating air is at a temperature of 140;t0. 250 F. or the treated yarns may be passed over one or more drying cans, which are heated at a temperature of 140 to 250 F., until the yarns are dry or contain less than 10% moisture.

The sized yarns are now ready for the weaving opera tion and may be woven in a loom at a relative humidity between about 40. and Any suitable yarn, such as nylon, cotton, acetate, viscose, wool, polyester yarns and the like, may be used as the filling in the weaving operation. The size adheres to the nylon yarns during the Weaving operation without splitting or dusting off and protects the yarns from the mechanically moving parts of a loom. This excellent adhesion of the size to the nylon yarns is particularly unexpected in view of the fact that alkali metal salts of the same interpolymers lack adhesion to nylon yarns during the weaving operation, and especially when it is considered that nylon yarns undergo considerable stretching and contraction in the loom and thus subject the size to considerable stretching and contraction. The interpolymer sizes disclosed herein are also sufficiently hard so that they dry on drying cans without sticking to the cans.

The sizev is readily removed from the warp yarns in the woven fabric by simply scouring with water, or soaping in a mild aqueous soap solution. This means that the fabric can then be treated with any suitable finishing agent to produce the desired finish on the fabric.

The term nylon as used herein is intended to include water-insoluble fiber-forming linear superpolyamides, particularly the water-insoluble fiber-forming linear polyamides prepared by condensing an aliphatic diamine such as hexamethylene diamine with an aliphatic polybasic acid such as adipic acid or sebacic acid, such as the polyamides described in United States Patents No. 2,071,250, No. 2,130,532 and No. 2,130,948. Of the foregoing linear polyamides, it is preferred to size the water-insoluble polyhexamethylene-adipamide warp yarns, or warp yarns prepared from. nylon obtained by condensation polymerization of caprolactam, since they are commercially available and are especially amenable to sizing by the methods of this invention.

While this invention has been described with particular reference to preferred embodiments, it will be appreciated that variations from the exact details given herein can be effected without departing from the invention in its broadest aspects.

We claim:

1. Nylon yarn sized with a water-soluble free acid form of a C -C olefin/maleicinterpolymer having from zero to percent of its maleic unitsmono-esterified with an alkanol, said interpolymer in said free acid form having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C.

2'. Nylon yarn sized with a C -C olefin/maleic anhydride interpolymer converted to water-soluble free acid form, said interpolymer in said free acid form having from zero to 100 percent of its maleic units mono-esterified with an alkanol, said interpolymer in said free acid form having a specific viscosity of at least about 0.1 as determined on a one weight per cent solution thereof in dirnethylformamide at 25 C.

3'. Nylon yarn sized with an ethylene/maleic anhydride interpolymer converted to water-soluble free acid form, said interpolymer in said free acid form having from zero to 100 percent of its maleic units mono-esterified with an alkanol, said interpolymer in said free acid form having a specific viscosity within the range of about 0.3 to 4 as determined on a one weight percent solution thereof in dimethylformamide at 25 C.

4. Nylon yarn sized with a propylene/maleic anhydride interpolymer converted to water-soluble free acid form, said interpolymer in said free acid form having from zero to 100 percent of its maleic units mono-esterified with an alkanol, said interpolymer in said free acid form having 15 a specific viscosity within the range of about 0.3 to 4 as determined on a one weight percent solution thereof in dimethylformamide at 25 C.

5. Nylon yarn sized with a C -C olefin/maleic anhydride interpolymer which has been esterified with a lower alkanol in an amount not exceeding 0.5 mole of said alkanol per mole of maleic anhydride in said interpolymer and converted to water-soluble free acid form, said interpolymer in said free acid form having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C.

6. Nylon yarn sized with an ethylene/maleic anhydride interpolymer converted to water-soluble free acid form and essentially consisting of regularly recurring units of the formula CHzCHzCH- CH- ()H ()H and having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C.

7. Nylon yarn sized with a propylene/maleic anhydride interpolymer converted to water-soluble free acid form and essentially consisting of regularly recurring units of the formula CH3 CH;( 3HCH-CH O: C=O

and having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C.

8. A method of sizing nylon yarn which comprises contacting same with an aqueous solution of a watersoluble free acid form of a C -C olefin/maleic interpolymer having from zero to 100 percent of its maleic units mono-esterified with an alkanol, said interpolymer in said free acid form having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C., said solution being supplied in a concentration and in an amount sufficient to deposit a sizing quantity of said interpolymer on said yarn, and then drying said yarn.

9. A method of sizing nylon yarn which comprises contacting same with a C -C olefin/maleic anhydride interpolymer converted to water-soluble free acid form, said interpolymer in said free acid form having from zero to 100 percent of its maleic units mono-esterified with an alkanol, said interpolymer in said free acid form having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C., said solution being supplied in a concentration and in an amount sufficient to deposit a sizing quantity of said interpolymer on said yarn, and then drying said yarn.

10. A method of sizing nylon yarns to prepare them for weaving which comprises treating said yarns with an aqueous solution comprising about 2 to percent by weight of an ethylene/maleic anhydride interpolymer converted to water-soluble free acid form, said interpolymer in said free acid form having from zero to 100 percent of its maleic units mono-esterified with an alkanol, said interpolymer in said free acid form having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at C., said aqueous solution being supplied in an amount sufiicient to deposit from about 0.5 to 5 percent by weight, based on the dry yarns, of said interpolymer, and then drying said yarns.

11. A method of sizing nylon warp yarns to prepare them for weaving which comprises treating said yarns with an aqueous solution comprising about 2 to 15 percent by weight of a propylene/maleic anhydride interpolymer converted to water-soluble free acid form, said interpolymer in said free acid form having from zero to percent of its maleic units mono-esterified with an alkanol, said interpolymer in said free acid form having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C., said aqueous solution being supplied in an amount suflicient to deposit from about 0.5 to 5 percent by weight, based on the dry yarns, of said interpolymer, and then drying said yarns.

12. A method of sizing nylon warp yarns to prepare them for weaving which comprises treating said yarns with an aqueous solution comprising about 2 to 15 percent by weight of a C -C olefin/maleic anhydride interpolymer converted to water-soluble free acid form, said interpolymer in said free acid form having from zero to 100 percent of its maleic units mono-esterified with an alkanol, said interpolymer in said free acid form having a specific viscosity within the range of about 0.3 to 4 as determined on a one weight percent solution thereof in dimethylformarnide at 25 C., said aqueous solution being supplied in an amount sufficient to deposit from about 0.5 to 5 percent by weight, based on the dry yarns, of said interpolymer, and then drying said yarns.

13. A method of sizing nylon yarns to prepare them for weaving which comprises treating said yarns with an aqueous solution comprising about 2 to 15 percent by weight of an ethylene/maleic anhydride interpolymer converted to water-soluble free acid form and essentially consisting of regularly recurring units of the formula and having a specific viscosity of at least about 0.1 as determined on a one weight percent solution thereof in dimethylformamide at 25 C., said aqueous solution being supplied in an amount sutficient to deposit from about 0.5 to 5 percent by weight, based on the dry yarns, of said interpolymer, and then drying said yarns.

14. Method according to claim 8, wherein said nylon yarn is prepared from polyhexamethylene-adipamide.

15. Method according to claim 8, wherein said nylon yarn is prepared from nylon obtained by condensation polymerization of caprolactam.

16. Sized nylon yarn according to claim 1, wherein said yarn is prepared from polyhexamethylene-adipamide.

17. Sized nylon yarn according to claim 1, wherein said yarn is prepared from nylon obtained by condensation polymerization of caprolactam.

18. Sized nylon yarn according to claim 6, wherein said yarn is prepared from polyhexamethylene-adipamide.

19. Sized nylon yarn according to claim 7, wherein said yarn is prepared from polyhexamethylene-adipamide.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Mat. 20,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,854,357 September 30, 1958 John H, Johnson et 211 It is hereby; certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line '74, for "monolkyl" read monoalkyl column 4, line 18, for "present" read w presence line 59, for "500 pounds" read 600 pounds column 14, line 24, for "simply" read simple column 15, line 59, after "nylon" insert Warp Signed and sealed this 19th day of April 1960.,

( SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

10. A METHOD OF SIZING NYLON YARNS TO PREPARE THEM FOR WEAVING WHICH COMPRISES TREATING SAID YARNS WITH AN AQUEOUS SOLUTION COMPRISING ABOUT 2 TO 15 PERCENT BY WEIGHT OF AN ETHYLENE/MALEIC ANHYDRIDE INTERPOLYMER CONVERTED TO WATER-SOLUBLE FREE ACID FORM, SAID INTERPOLYMER IN SAID FREE ACID FORM HAVING FROM ZERO TO 100 PERCENT OF ITS MALEIC UNITS MONO-ESTERIFIED WITH AN ALKANOL, SAID INTERPOLYMER IN SAID FREE ACID FORM HAVING A SPECIFIC VISCOSITY OF AT LEAST ABOUT 0.1 AS DETERMINED ON A ONE WEIGHT PERCENT SOLUTION THEREOF IN DIMETHYLFORMAMIDE AT 25*C., SAID AQUEOUS SOLUTION BEING SUPPLIED IN AN AMOUNT SUFFICIENT TO DEPOSIT FROM ABOUT 0.5 TO 5 PERCENT BY WEIGHT, BASED ON THE DRY YARNS, OF SAID INTERPOLYMER, AND THEN DRYING SAID YARNS. 